But now a prominent art expert and historian believes the subterranean site is likely to have been a Druid temple dating back more 2000 years.

Julian Spalding, the former head of Glasgow’s museums and galleries, claims that the temple was deliberately buried by the ancient priests to protect its sacred nature.

And he believes further work at Gilmerton Cove, which was opened as a visitor attraction 13 years ago, could unlock a host of secrets about the mysterious labyrinth.

Experts have long been baffled by the origins of Gilmerton Cove, which feature several stone tables and chairs. Theories over past uses have including a witches coven, an illicit whisky still, a drinking den and even the home of an exclusive 18th century “Hellfire Club.”

Official records show Gilmerton Cove was created by a local blacksmith, George Paterson, in 1724. But Mr Spalding is convinced he simply dug out rubble used to fill in the remains of the temple.

He said: “It is very probable that the whole complex was deliberately buried, a widespread ancient practice which prevented the subsequent defilement of sacred sites. This interpretation explains why two passages are still blocked by unexcavated rubble. It is inexplicable why Paterson should have filled them up after going to the immense trouble of excavating them.

“The work is beautifully consistent throughout and indicates a team of highly-skilled craftsmen, with numerous assistants, guided by a mastermind. The arrangement of rooms and passages is elaborate and the dividing walls are often remarkably thin.

“All the shapes within the Cove are womb-like and curved, indicating a Celtic or even earlier culture.”

Mr Spalding claims the site, which lies beneath a betting shop, is likely to date back to the Iron Age and is of huge international significance because it is such a uniquely-good condition. He wants the site to be considered for world heritage status, like Edinburgh’s Old and New Towns.

Mr Spalding added: “The identification of Gilmerton Cove as a Druid temple makes sense of all the evidence.

“Druids were known to meet in secret in woods and caves away from habitation. Gilmerton is on a high ridge, marked with megaliths, overlooking Cramond, the site of mankind’s earliest settlement in Scotland, and, later, a Roman Fort.

“If it is a Druid temple, discovered by chance in the 18th Century, then it will be the first substantial archaeological evidence of this sophisticated and highly-secretive priesthood.”